STK1000 have an external DAC with an integrated amplifier. The external DAC can be used to drive a headset or the on board speaker.
The output of the AT73C213 DAC can be connected to the stereo phones jack by changing the audio jumper settings. The on-board speaker is always connected to the amplifier. The output of this speaker is also connected to the 2-pin connector JP7.
Refer the help files of the daughter board to find out what interfaces are used and which peripheral on the processor are connected to the interface.